First, with the ignition switch turned on and the wiper switch set to "low" or "high", tug lightly on the wiper arm. If the motor starts to run, it has a bad ground. If it doesn't run, continue on:
Turn on the ignition switch, and turn the wiper switch to "low" or "high", not the delayed settings. Grab a test light, ground the wire on the battery negative post, then touch the probe to the metal case of the wiper motor. Don't be startled if the motor starts to run. If the test light lights up, there is proof of a bad ground for the motor. To eliminate the vibration from being transmitted into the passenger compartment, the motor is bolted to a plate that is mounted on three rubber feet. A brass ground strap is riveted to that plate and goes to one of the mounting bolts. Over time, the high current overheats that ground connection and arcing occurs. The permanent fix is to add a new ground wire between that mounting plate and the body of the car. Older wiper motors used five screws to hold the round switch plate to the motor housing. You could use one of those screws to bolt the new ground wire to. Newer motors use rivets instead of screws. For that style it is easier to just drill a small hole in the mounting plate and run a self-tapping screw in there to attach the new ground wire.
Saturday, January 22nd, 2011 AT 6:35 PM